Stratigraphic Analysis of Nebkas for Detecting Climatic Fluctuations (Case study: Ala Basin in the Border of Central Desert of Iran)

Wind deposits are a major source of long-standing environmental information and stratigraphy and ýsedimentology of the sand dunes can be used to interpret past events due to increased wind ýactivity. Stratigraphic and sedimentary elements of sand dunes such as Paleosoal and clay ýdensity can serve as indicators of climate change and provide useful evidence for the ýreconstruction of past environments in arid regions. Given that very limited information is available on the characteristics of the ancient climates of dry and desert regions of Iran, the stratigraphy of sediments in the hills and nebkas of these regions can help to understand the past climate of the region. In this research we investigated effects of climate change on the characteristics of nebka layers and ýtry to reconstruc Paleoclimatic of nebkas in Ala basin in the Semnan Province.ý The method of this research is based on field and laboratory studies as well as data analysis of the observation wells and wind data of this basin. ýThe results showed that nebka layers are thicker in newer layers than the older ones, that ýimplies more sedimentation in recent periods due to increase in groundwater levels and during periods of drought in ýthe region as well as more material removal and deposited by wind around nebkas that ýis due to the decrease in groundwater levels which has significant impact on nebka's layers and ýstratums. As the groundwater level decreases, the amount of adhesion of the sedimentary particles of the strains decreases due to the availability of reduced moisture content, and if this subsidence of groundwater continues to persist, over the years, the condensation of these impurities becomes a corrosive environment. Considering the prevailing winds the strongest and in the basin, the southeastern and southern marginal cities of this nebka are exposed to dust storms resulting from the erosion of exploration of these nebkas